Traction motor gear lubricant



April 9, 1966 J. R BURTON ETAL 3,247,112

TRACTION MOTOR GEAR LUBRICANT Filed April 18, 1965 Emu/279 7/019, /Vau/'s.

United States Patent 3,247,112 TRACTION MOTOR GEAR LUBRICANT James R. Burton, Groves, Edward A. Cross, Beaumont,

John H. Greene, Groves, and Fred T. Crookshank,

Port Arthur, Tex, assignors to Texaco Inc., New York,

N.Y., a corporation of Delaware Filed Apr. 18, 1963, Ser. No. 273,873 9 Claims. (Cl. 25242) This invention relates to lubricating compositions of improved lubricating properties which are particularly suitable for use as traction motor gear lubricants, containing a highly oxidized petroleum oxidate.

A traction motor gear lubricant comprising a relatively lightly oxidized paraffinic residual oil as substantially the sole oil component, thickened by a small amount of alkali metal soap, is describe-d by Cro-okshank et al. in US. 2,789,091. It was found that a combination of improved low temperature properties, superior resistance to oxidative thickening and other advantages were obtainable in this composition, which were not obtainable in other compositions of various types which had been employed as traction motor gear lubricants previously. However, specifications more recently adopted by diesel engine manufacturers include a requirement that the oil component have a minimum viscosity of 1500 Saybolt Universal seconds at 210 R, which is not met in the compositions of Crookshank et al. In addition, the specifications have included a requirement for greatly improved bearing leakage properties in traction motor gear lubrication over those obtainable in lubricant compositions employed for this purpose heretofore.

The lubricant compositions of this invention comprise essentially a mixture of a paraffinic residual oil and about '2060 percent by weight of a highly oxidized petroleum oxidate, sufficient to provide a mixture having a Saybolt Universal viscosity at 210 F. from 1500 to about 300 seconds, and about 1-5 percent by weight of an alkali metal fatty acid soap. The preferred compositions comprise a mixture of lubricating oil with about 25-45 percent by weight of the oxidate, sufficient to give a Saybolt Universal viscosity at 210 F., in the range from 1500 to about 2500 seconds, and thickened to an N.L.G.I. No. 0 grade consistency with about 24.5 percent by weight of sodium fatty acid soap.

We have found that the above compositions provide the combination of properties required in a superior traction motor gear lubricant, including the low bearing leakage required to meet the new industrial specifications in addition to improved resistance to oxidation, low temperature properties required for cold starting at low temperatures, and good adhesion to the bearings and lubricating properties generally. The discovery that this desired combination of properties was obtainable in these compositions was unexpected, since other oxidate containing compositions having the required oil component viscosity of 1500 seconds minimum at 210 F. are lacking in the required low bearing leakage and are also particularly deficient in oxidation resistance properties.

The sole figure shows graphically the bearing leakage properties in the Traction Motor Gear Leakage Test for a representative lubricating composition of this invention (A) in comparison with those obtained in the same test upon three commercial lubricants employed as traction motor gear lubricants.

Parafiinic residual oils which may be employed in these compositions are those having Saybolt Universal viscosities in the range from about 150 seconds to about 350 seconds, and preferably from about 175 seconds to about 275 seconds at 210 F. They are most suitably substantially dewaxed oils, having pour points below about 60 F., and preferably below about 40 F. They may comprise blends of lower and higher viscosity oils having viscosities in the range from about seconds to about 750 seconds at 210 F., preferably comprising a major proportion of an oil in the viscosity range from about to about 350 seconds. Very advantageously, an oil blend having a viscosity in the range from about seconds to about 275 seconds at 210 P. which comprises about 10 to 30 percent by weight of a paratfinic residual oil having a viscosity in the range from about 350 to about 550 seconds at 210 F. may be employed. We have found that such blends are employed with special advantage in the preparation of N.L.G.I. No. 0 grade products having a maximum soap content of 2.5 percent as required to meet certain industrial specifications.

The oxidates employed are asphaltic materials obtained by blowing paraffinic residual oils in the upper lubricating oil viscosity range, such as from about 90 to about 750 seconds Saybolt Universal at 210 F., preferably from about 150 to about 350 Saybolt Universal seconds at 210 F. The oxidation may be carried out in the conventional manner, by blowing with air at an elevated temperature in about the range 400-600 F., in the presence or absence of a catalyst until a product having a ring and ball softening point of at least about 250 F. is obtained. It is preferably carried out by blowing at a temperature of about 400500 F. until a product having a ring and ball softening point in about the range 275350 F. is obtained. These products ordinarily have penetrations at 77 F. in about the range 30100, pr ferably in about the range 4080, and contain about 10-40 percent by weight of asphaltenes.

The alkali metal fatty acid soap in preferably a sodium or lithium soap of a fatty acid or fatty acid mixture containing about 1422 carbon atoms per molecule, such as palmitic acid, stearic acid, oleic acid, 12-hydroxystearic acid, etc., obtained by saponification of the corresponding fatty acids, their glycerides or other esters. A particularly suitable soap for this purpose is sodium tallowate.

The preparation of the grease composition may be carried out in any suitable manner. It is preferably carried out by saponifying the saponifiable material with an alkali metal base in the presence of a portion of the lubricating oil employed in the grease, heating to a higher temperature and then blending in the remainder of the lubricating oil and the oxidate, the latter being added to the grease at a temperature above the melting point of the oxidate. Following the oxidate addition, the grease mixture is preferably heated to a temperature substantially above the melting point of the oxidate, such as at a temperature above about 300 F. in order to obtain complete blending of the oxidate into the composition. For convenience, the oxidate may be employed in the form of a blend with a portion of the lubricating oil employed in the grease, prepared by heating the oxidate to a temperature above its melting point, suitably above about 400 F., and then blending the lubricating oil into the melted oxidate.

The following examples are given for the purpose of further disclosing the invention.

EXAMPLE I A lubricating grease having the following composition in percent by weight:

Sodium tallowate 3.9 Oxidate 30.9 Lubricating oil 65.2

The saponifiable material employed in the preparation was a commercial hard tallow, having a saponification number of 194, an iodine number of 52 and containing 5.8 percent of free fatty acids, as oleic acid.

The lubricating oil employed was a 21.9 API gravity refined paraffinic residual oil having a flash point, COC

3 (Cleveland Open Cup), of 565 F., a fire point, COC, of 660 F., a pour point of F. and a Saybolt Universal viscosity at 210 F. of 199 seconds.

The oxidate employed was a product having a penetration at 77 F. (AS113) of 47, a melting point (AS-18) of 299 F., and an asphaltene content of about 27 percent, obtained by oxidizing a raw residuum from a paraffin base crude having a Saybolt Universal viscosity at 210 F. of about 230 seconds and containing about 1.3 percent of asphaltenes. The oxidation was carried out by blowing the residuum with air for about 59 hours at 430-470 F., employing an air rate providing a large excess of oxygen over that taken up in the reaction.

Following is a detailed description of the method of preparation employed: A steam heated paddle stirred laboratory kettle was charged with 14.56 pounds of tallow, 2.0 pounds of water and 10 pounds of lubricating oil, the mixture heated with stirring to 140 F. and 4.17 pounds of 49 percent aqueous caustic solution added. The mixture was then further heated with stirring to 323 F. and 26.2 pounds additional lubricating oil added gradually over a period of one hour and 35 minutes while the mixture was allowed to cool to 230 F. A second kettle of the same type was charged with 17.0 pounds of the soap base obtained as described above, and the soap base reheated with stirring to 245 F. Addition of the oxidate in the form of small pieces was then begun and 32.5 pounds of the oxidate added in this manner over a period of 3 hours and 43 minutes while the temperature was increased gradually to 312 F. Additional lubricating oil was then added gradually over a period of one hour and 27 minutes until 32.5 pounds of additional oil had been added, while the temperature was maintained at 312318 F. The mixture was further heated to 341 F. in 30 minutes and then allowed to cool. An additional 36.1 pounds of lubricating oil and 6.4 pounds of oxidate (added in the form of a preformed oil blend) were blended into the composition at about 205242 F. during the finishing to obtain the desired penetration. The product was finally drawn at 197 F. and pumped through a 100 mesh screen.

A glossy black soft stringy grease was obtained as described above, having the combination of lubricating properties required for a very superior traction motor gear lubricant, including the oil component viscosity and low bearing leakage required by diesel engine manufacturers specifications.

EXAMPLE II A lubricating grease having the following composition in percent by weight:

Sodium tallowate The lubricating oil employed was a blend in about a 2:1 ratio by weight respectively of a parafi'inic residual oil described in Example I and a heavier paraifinic vacuum residuum having a Saybolt Universal viscosity at 210 F. of about 470 seconds.

The saponifiable material and the oxidate employed in the preparation were the same as those described in Example I.

The grease preparation was carried out substantially as described in Example I.

The product obtained in this preparation was a soft black stringy grease having the desired combination of lubricant properties for a superior traction motor gear lubricant.

The data given in Table I below show that the particularly desired combination of low bearing leakage and good low temperature properties, in addition to high Working stability and the required oil component viscosity characteristics were obtained in the greases described in Examples I and H.

Table l ExampleI Example Require- II merits AS'IM Penetration at 77 F.:

Unworked Worked, 60 strokes Worked, 100,000 str0kes Simulated TM GL Torque Test at 40 EMD Leakage Test:

Leakage, lbs afte Viscosity of O' SSU/210 F Pass.

}Little or none 1,500 min.

1 Obtained upon a plant batch.

The simulated TMGL Torque Test is a test for evaluating the low temperature starting characteristics of a lubricant. It is run in a washing machine transmission, the power required for starting the unit lubricated with the test lubricant and cooled to the test temperature being determined by means of a recording watt meter. The test is considered a failure when the starting power exceeds 4,000 watts, when the electric motor smokes on starting or when the motor is on starting windings for more than 20 seconds.

The EMD Leakage Test is carried out in a standard TMG set and gear case charged with 10 pounds of the test lubricant. The test is run at no load and an axle speed of 600 r.p.m. for 24 hours, with heat applied to the gear case during the first 8 hours of the test to maintain the lubricant at a temperature of 210-220 F. The lubricant is rated by the amount of lubricant which leaks through the annular clearance between the rotary pinion gear shaft and stationary pinion cover ring and out a drain space in the pinion bearing cover.

The results obtained in the EMD Leakage Test with the grease described in Example II are shown graphically in 'FIG. 1 in comparison with the results obtained upon commercial traction motor gear lubricants of different types. Graph A was constructed from the data obtained upon the grease described in Example II. Graph B was constructed from data obtained upon a commercial gear lubricant of the blown asphalt type, comprising a blown asphalt residuum and a parafiinic lubricating oil residuum, the blend having a Saybolt Universal viscosity at 210 F. in the range 1850-2200 seconds. Graph C was constructed from data obtained from a commercial traction motor gear lubricant comprising an asphaltic residuum thickened with about 3 percent by weight of sodium tallowate. Graph D was constructed from data obtained from a commercial traction motor gear lubricant comprising a propane resin having a Saybolt Universal viscosity at 210 F. of about 3500 seconds, thickened with about 3.8 percent by weight of sodium soap.

As shown by the figure, the lubricating compositions of our invention were outstandingly superior to commercial traction motor gear lubricants in their hearing leakage characteristics, including particularly the oxidatecontaining compositions of the prior art employed as traction motor gear lubricants.

Table II below shows the high oxidation resistance properties of the greases of our invention as determined by the Modified U.S. Gear Thickening Test, in comparison with the results obtained in the same test upon other compositions prepared from high viscosity oils as required by the industrial specifications. Lubricants Nos. 1 and 2 of the table are the greases described in Examples I and II, respectively. Lubricant No. 3 is a grease of the same composition except that a 4000 viscosity blend of the oxidate and lubricating oil was employed. Lubricant No. 4 is an unblended oxidate obtained in the same manner and from the same starting material as the oxidate employed in Examples I and II, except that the oxidation was carried out for a shorter time. Lubricant No. 5 is a grease of the same composition as that d sclosed in Example I of U.S. 2,789,091, except that a more highly oxidized oil was employed in order to meet the requirement for a higher viscosity oil component. Lubricant No. 6 comprises an oxidized oil of the same character as that employed in the composition of Example I of U.S. 2,789,091 together with 25 percent by weight of propane resins having a Saybolt Universal viscosity at 210 F. in the range 11,000-14,000 and a penetration at 770 F. of about 194.

Table II MODIFIED U.S. GEAR LUBE THICKENING TEST ASTM Worked Pene. at 77 F. N 0. Oil Component Original Percent Change 1. 2200 viscosity blend of oxidate and lub- 373 -2. 2

ricating oil. 2. 1969 viscosity blend of oxidate and lub- 359 2. 7

rieating oil. 3. 4000 viscosity blend of oxidate and lub- 374 --6. 1

ricating oil. 4. 1800 viscosity oxidized residuum 367 1 TH 5 2000 viscosity oxidized lubricating oil 346 1 TH 6 1863 viscosity blend of oxidized lubri- 380 1 TH eating oil and petroleum resins.

1 Too heavy to work in the grease worker.

The Modified U.S. Steel Corporation Gear Lube Thickening Test is carried out by passing 10 liters of dry air through 300 ml. of the test lubricant for 310 hours while the lubricant is maintained at 203 F. At the end of this period the penetration is again determined and the resistance of the composition to oxidative change is indicated by the amount of penetration change.

As shown by the data given in Table II, the greases of our invention were highly resistant to oxidative change, in marked contrast to other compositions containing oxidized oils or oxidate-lubricating oil blends meeting the viscosity requirements of the industrial specifications. The unexpected nature of this effect is shown particularly by the fact that a less highly oxidized oxidate of the same character otherwise as that employed in the compositions of Examples I and Ii was highly susceptible to oxidative thickening (Lubricant No. 4), while a composition which was highly susceptible to oxidative thickening was also produced by substituting a more highly oxidized oil of the same character otherwise for the lightly oxidized oil in the composition of Crookshank et al. (Lubricant No. 5). Furthermore, attempts which have been made to remedy the oxidation instability in the latter composition by means of various oxidation inhibitors of generally high effectiveness have been unsuccessful.

The grease composition of Example I has been employed very successfully in the lubrication of 3 diesel locomotives equipped with EMD SD124 standard gear cases in railway service for several months, confirming that this lubricant has the required combination of low bearing leakage and superior resistance to oxidation in addition to the other lubricating properties required in this service.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and

therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A gear lubricant comprising about 1-5 percent by weight of an alkali metal soap thickening agent and a blend comprising about 40-80 percent by weight of an unoxidized parafiinic residual oil having a Saybolt Universal viscosity at 210 F. in about the range 150-350 seconds, and about 20-60 percent by weight of a petroleum oxidate having a penetration at 77 F. of about 30-100, obtained by air blowing a parafiinic residual oil having a viscosity in the lubricating oil range, said blend having a Saybolt Universal viscosity at 210 F. from about 1500 to about 3000 seconds, said amount of soap being sufficient to thicken said oil blend to a grease consistency.

2. The lubricant of claim 1 wherein said unoxidized paratfinic residual oil has a Saybolt Universal viscosity at 210 F. of about 175-275 seconds.

3. The lubricant of claim 1 wherein said unoxidized paraffinic residual oil is a blend of -90 percent by weight of a parafiinic residual oil having a Saybolt Universal viscosity at 210 F. of about 175-275 seconds and about 10-30 percent by weight of a paraffinic residual oil having a Saybolt Universal viscosity at 210 F., of about 350 to about 550 seconds.

4. The lubricant of claim 1 wherein the said soap is sodium soap.

5. The lubricant of claim 4 wherein the said sodium soap is sodium tallowate.

6. The lubricant of claim 1 wherein the said petroleum oxidate has a penetration at 77 F. of about 40-80 seconds.

7. A gear lubricant consisting essentially of a blend comprising about 25-45 percent by weight of an oxidized paraffinic residual oil having a penetration at 77 F. of about 30-100 and about 55-75 percent by weight of an unoxidized parai'linic residual oil having a Saybolt Universal viscosity at 210 F. of about -350 seconds and a pour point below about 40 F., thickened to an N.L.G.I. No. 0 grade consistency by about 2-4.5 percent by weight of a sodium fatty acid soap, said blend having a Saybolt Universal viscosity at 210 F. in the range from 1500 to about 2500 seconds.

8. The lubricant of claim 7 wherein the said sodium soap is sodium tallowate.

9. The lubricant of claim 7 wherein the said unoxidized paraflinic residual oil comprises about 70-90 percent by weight of an oil having a Saybolt Universal viscosity at 210 F. of -275 seconds and about 10-30 percent by Weight of a parafiinic residual oil having a Saybolt Universal viscosity at 210 F. of about 350-550 seconds.

References Cited by the Examiner UNITED STATES PATENTS 2,789,091 4/1957 Crookshank et al 252-42 2,814,595 11/1957 Bearbower et al. 25255 X 2,870,089 1/1959 McGrogan 25242 X 3,074,884 1/1963 Pitman 25255 X 3,095,375 6/1963 Pitman 252-21 DANIEL E. WYMAN, Primary Examiner. 

1. A GEAR LUBRICANT COMPRISING ABOUT 1-5 PERCENT BY WEIGHT OF AN ALKALI METAL SOAP THICKENING AGENT AND A BLEND COMPRISING ABOUT 40-80 PERCENT BY WEIGHT OF AN UNOXIDIZED PARAFFINIC RESIDUAL OIL HAVING A SAYBOLT UNIVERSAL VISCOSITY AT 210*F. IN ABOUT THE RANGE 150-350 SECONDS, AND ABOUT 20-60 PERCENT BY WEIGHT OF A PETROLEUM OXIDATE HAVING A PENETRATION AT 77*F. OF ABOUT 30-100, OBTAINED BY AIR BLOWING A PARAFFINIC RESIDUAL OIL HAVING A VISCOSITY IN THE LUBRICATING OIL RANGE, SAID BLEND HAVING A SAYBOLT UNIVERSAL VISCOSITY AT 210*F. FROM ABOUT 1500 TO ABOUT 3000 SECONDS, SAID AMOUNT OF SOAP BEING SUFFICIENT TO THICKEN SAID OIL BLEND TO A GREASE CONSISTENCY. 